This spring has brought us cool weather, wet/dry spells, and now potassium deficiencies. We have mainly been hearing about corn and soybean potassium deficiencies on the Macon Ridge. However, this does not mean that they are not showing up throughout our alluvial soils.
Potassium is very important for water use efficiency in crops. This means that irrigation on the fields showing deficiency symptoms will need to be managed diligently. There are a few reasons that symptoms could be showing up: 1) Dry soils, 2) Compaction, 3) Low soil test K, and 4) Reduced early-season root growth. Potassium cannot be taken up efficiently in the soil without the presence of water, which can cause a deficiency to appear even if adequate potassium was applied to the soil. Compaction can also cause a potassium deficiency to appear because the roots are not able to find enough potassium in the un-compacted soil. If a soil sample is collected and the results show that the soil is low in potassium, then the recommended amount of potassium should be applied after the current cropping season. Lastly, due to some of the weather that was experienced this spring, there could have been reduced root growth in spots affected by standing water or cold weather. This reduced root growth creates a smaller zone of potassium available to the plants.
Deficiency symptoms in corn and soybeans are denoted by edge of leaf necrosis.
Currently, the LSU AgCenter soil fertility research group does not currently have data on the yield benefits of foliar-applied potassium. Furthermore, research throughout the region has shown little to no yield benefits for foliar potassium applications. Additionally, if yield benefits are seen, there is a chance that the cost of application will often outweigh any yield benefit. Therefore, caution should be used prior to any in-season foliar potassium application. If a foliar K is going to be added, follow the label carefully due to the chance of leaf burn.
If you have any questions, please contact:
Beatrix Haggard, Northeast Region Soil Specialist: (318) 498-2967
Josh Lofton, Agronomist: (318) 498-1934
Dan Fromme, Corn and Cotton Specialist: (318)880-8079